In recent years, electronic devices such as cellular phone, PHS (Personal Handy phone System), PDA (Personal Digital Assistant) and the like have been size-reduced, weight-reduced and highly-functionalized. As a result, not only the communication-related functions such as calling and mailing but also the functions comparable to a computer, such as camera, music reproduction, television and the like have been embedded therein.
Accompanied with the high-functionalization, there are needs for increasing a screen size of a display area so as to use various applications comfortably. However, since a size of a housing is limited in an electronic device that is being miniaturized, an area that is allotted to an operation unit is inevitably reduced in attempts to increase the screen size of the display area. Accordingly, the same operation key should be assigned with various functions or a hierarchy of menus should be deepened, so that the operability is lowered.
Patent Document 1 discloses a technique in which a first touch sensor is provided on the same face as a screen (information display screen) and a second touch sensor is provided on an opposite face and is used as an auxiliary input means for fingerprint authentication and the like.